Fluorinated Silica Nanoparticles Research Articles

Wettability alteration properties of fluorinated silica nanoparticles in liquid-loaded pores: An atomistic simulation

Control over the wettability of reservoir rocks is of crucial importance for enhancing oil and gas recovery. In order to develop chemicals for controlling the wettability of reservoir rocks, we present a study of functionalized silica nanoparticles as candidates for wettability alteration and improved gas recovery applications. In this paper, properties of fluorinated silica nanoparticles were investigated in water or decane-loaded pores of mineral silica using molecular dynamics simulation. Trifluoromethyl groups as water and oil repellents were placed on the nanoparticles. Simulating a pore in the presence of trapped water or decane molecules leads to liquid bridging for both of the liquids. Adsorption of nanoparticles on the pore wall reduces the density of liquid molecules adjacent to the wall. The density of liquid molecules around the nanoparticles decreases significantly with increasing the number of trifluoromethyl groups on the nanoparticles’ surfaces. An increased hydrophobicity of the pore wall was observed in the presence of adsorbed fluorinated silica nanoparticles. Also, it is observed that increasing the number of the trifluoromethyl groups results in weakening of liquid bridges. Moreover, the free energy of adsorption on mineral surface was evaluated to be more favorable than that of aggregation of nanoparticles, which suggests nanoparticles adsorb preferably on mineral surface.

Emulsions of fluorinated oils stabilised by fluorinated silica nanoparticles

Stabilisation of perfluorohexane (PFH)-in-water emulsions was investigated using (i) fumed silica nanoparticles having different levels of hydrophobicity and (ii) fluoroalkyl-grafted silica nanoparticles of different degrees of fluorophilicity. Hydrophilic silica nanoparticles failed to stabilise these emulsions, whereas particles with intermediate levels of hydrophobicity gave rise to stable water-in-oil emulsions. A series of fluorinated silica nanoparticles were prepared via a silylation reaction between hydrophilic silica nanoparticles and a fluoroalkyl-monochlorosilane. Elemental analysis and 29Si solid-state NMR on the derivatized particles were carried out and grafting densities of the attached fluoroalkylsilyl (F-silyl) were calculated. A series of fluoroalkyl-grafted silica nanoparticles with a grafting density ranging from about 0.4–1 gps nm−2 was obtained. The type and stability of fluorinated oil and water emulsions stabilised by the prepared fluorinated silica were investigated as a function of the particle fluorophilicity, the particle concentration, the oil type and the oil to water volume ratio. The modified fluorosilica particles are more effective in stabilising perfluorohexane-in-water emulsions than the unmodified ones and the emulsion stability increases as the particle concentration increases. The contact angle of water in air on compressed discs of the fluorosilica particles increases as the degree of fluorination increases. Emulsions of perfluorohexane-in-water stabilised by FS-36 silica particles, having 36% F-silyl, were the most stable. The calculated and the measured contact angles of fluorosilica particles at the PFH-water interface were found to correlate with the observed emulsion types and their stabilities. The current work demonstrates that stable Pickering fluorinated oil-in-water emulsions are achievable using fluoroalkyl-grafted silica nanoparticles.

Synthesis of fluorinated silica nanoparticles containing latent reactive groups for post-synthetic modification and for tunable surface energy.

A new PFCP-based chlorosilane monomer containing a latent reactive fluorine atom was synthesized utilizing a hydrosilylation reaction. This monomer was used to functionalize Stöber silica nanoparticles, or network silicas, and the ability to tailor the properties of the functionalized nanoparticles was investigated by reacting the latent reactive fluorinated alkene with various nucleophiles. In order to model the chemical transformations occuring with the PFCP-functionalized particles, a new PFCP-containing molecular silica was prepared using a hydrosilylation reaction. The molecular silica was designed such that it contained a latent reactive fluorine atom and could also undergo post-synthetic modifications with various nucleophiles. The ability to modify the latent reactive group and tune the properties of the molecular and network silicas was verified by multi-nuclear NMR ((1)H, (13)C, (19)F, and (29)Si), thermal characterizations, and by investigating the hydrophobicity and surface morphology of spin-cast films prepared from the molecular and network silicas.

Electrowetting on superhydrophobic natural (Colocasia) and synthetic surfaces based upon fluorinated silica nanoparticles

In this study, we look at alternative coatings to be used in DMF EWOD applications, specifically a natural surface, and synthetic fluorinated silica nanoparticle (FSNP) surfaces. Electrowetting on dielectric (EWOD) is a popular digital microfluidic (DMF) actuation approach, where droplets are moved over a series of electrodes. Hydrophobic coating is required to lower surface friction and enhance droplet movement over the surface. FSNPs are synthesized by a modified Stöber method, with different sizes of nanoparticles (5 to 150nm) and various degrees of fluorination (0 to 90%). These FSNP coatings and natural superhydrophobic surface, Colocasia leaf, were characterized with SEM and tested for their EWOD performance, i.e. EWOD voltage and contact angle change. Colocasia leaf required voltages of >300V for EWOD, whereas the performance of the FSNP coatings with varying nanoparticle sizes and degrees of fluorination show EWOD with voltages as low as 20V. The robustness of the FSNP surfaces was demonstrated by using various organic solvents, and longevity data is also presented.

Magnetic droplet actuation on natural (Colocasia leaf) and fluorinated silica nanoparticle superhydrophobic surfaces

Interest in digital microfluidics (DMF), where discrete droplets are manipulated in a miniaturized device, has grown rapidly due to the versatility that arises from non-linear control of fluids. Adding superparamagnetic particles to the fluid allows the droplet to be manipulated by magnetic fields, such as that from a simple permanent magnet, removing some of the complexity of previous DMF devices and adding enhanced robustness. The magnetic field strength need not be high to control commercially available magnetic silica microparticles, however a hydrophobic surface is required to provide reduced friction. In this study, three types of hydrophobic surfaces were explored for their use in the magnetic actuation of water droplets containing magnetic particles. A conventional fluoropolymer film was found to have excessive frictional resistance to effectively actuate droplets. A natural superhydrophobic surface, the Colocasia leaf, was found to have too much surface microstructure to allow the magnetic particles to move freely over the surface. The commercially available Ultra-Ever Dry®, on the other hand, was suitable for effective magnetic actuation of aqueous and mixed droplets as it provided a robust, virtually frictionless surface. Based on fluorinated silica nanoparticles, this surface allowed a 20μL water droplet to be manually pulled by a magnet at speeds in excess of 550mms−1.

Facile preparation in two steps of highly hydrophobic coatings on polypropylene surface

Monolayer and bilayer coatings deposited on polypropylene (PP) surface were prepared by sol–gel process at room temperature. Monolayer coatings were produced from sol–gel acidic solutions, containing tetraethylorthosilicate (TEOS) and different co-precursors such as phenyltriethoxysilane (PhTES), octylmethyldimethoxysilane (OMDMS) and dodecyltriethoxysilane (DOTES). Bilayer coatings consist of one layer prepared in a similar way described for monolayer coatings, followed by a second layer, obtained from fluorinated silica nanoparticles dispersion. The fluorinated group has been confirmed by the presence of CF bonds along with network SiOSi vibrational mode. Water contact angle values registered for bilayer-coated polypropylene are higher, comparing with the reference (pristine PP) and with the monolayer-coated substrate, and varies as a function of the hydrophobic functional groups of the silica co-precursors: phenyl<octyl<dodecyl. The fluorooctyl functions lead to a significant decrease in the surface energy values for bilayer coating, with very small values of polar component.

Spray coating of superhydrophobic and angle-independent coloured films

Angle-independent coloured films with superhydrophobicity were fabricated from quasi-amorphous arrays of monodispersed fluorinated silica nanoparticles via one-step spray coating. The film exhibited a high contact angle (>150°) and a low roll-off angle (~2°) and the colour could be tuned to blue, green and moccasin by varying the size of the nanoparticles.

Study on the Fabrication of Superhydrophobic Microporous Polypropylene Flat Membrane Using &lt;i&gt;In Situ&lt;/i&gt; Synthesis of Modified Fluorinated Silica Nano Particles

The wettability is the most important features of membrane, when it works as contactors. Although the membrane contactors offer many advantages over conventional contacting equipments, additional mass transfer resistance is introduced when micropores are filled with aqueous absorbents. Therefore, fabrication of superhydrophobic membrane which prevents diffusion of aqueous absorbent into membrane pores is a highly challenging task. In this work, superhydrophobic polypropylene (PP) membrane was fabricated using in situ synthesis of silica nano particles via thermally induced phase separation (TIPS) method. Flat sheet fabricated PP membranes were casted with methanolic solution containing various ratios of perfluorooctyltriethoxysilane (PFOTES)/ tetraethylortosilicate (TEOS) and then sol-gel reaction between the mixed silances was completed. The contact angle of coated membrane was reached to 168 degree, when the percentage of PFOTES/TEOS was fixed at 50% (mol/mol). Interestingly, due to the microporous structure of PP membrane, the synthesized fluorinated silica nanoparticles were observed on the surface as well as in the cross-sectional area of the membrane. Field emission scanning electron microscopy (FE-SEM) images were confirmed this point. Chemical structure of the coated membranes with 50% PFOTES was compared with pure PP membrane using ATR-IR. In order to evaluate the operational performance, coated membranes were immersed in aqueous solutions of mono ethanol amine (MEA), di ethanol amine (DEA) and pure water. In comparison with pure PP membrane, obtained results showed that the wettability of coated membranes was considerably decreased.

Synthesis of fluorinated nano-silica and its application in wettability alteration near-wellbore region in gas condensate reservoirs

Fluorinated silica nanoparticles were prepared to alter rock wettability near-wellbore region in gas condensate reservoirs. Hence fluorinated silica nanoparticles with average diameter of about 80nm were prepared and used to alter limestone core wettability from highly liquid-wet to intermediate gas-wet state. Water and n-decane contact angles for rock were measured before and after treatment. The contact angle measured 147° for water and 61° for n-decane on the core surface. The rock surface could not support the formation of any water or n-decane droplets before treatment. The functionalized fluorinated silica nanoparticles have been confirmed by the CF bond along with SiOSi bond as analyzed by FT-IR. The elemental composition of treated limestone core surface was determined using energy dispersive X-ray spectroscopy analyses. The final evaluation of the fluorinated nanosilica treatment in terms of its effectiveness was measured by core flood experimental tests.

Synthesis of Fluorinated Silica Nanoparticles and the Wetting Prevention Ability

Fluorinated silica nanoparticles (FSNs) were synthesized by the hydrolysis of tetraethyl orthosilicate and fluoroalkyl siloxane, and by the assistance of surfactant of cetyltriammonium bromide (CTAB) under basic condition. Through adjusting the synthesis conditions, the better particles distribution of fluorinated silica could be obtained. Then the FSNs were used to prepare liquid marble with water and the stability of the liquid marble was tested to investigate the wetting prevention ability of the fluorinated silica nanoparticles.

Fluorine Based Superhydrophobic Coatings

Superhydrophobic coatings, inspired by nature, are an emerging technology. These water repellent coatings can be used as solutions for corrosion, biofouling and even water and air drag reduction applications. In this work, synthesis of monodispersive silica nanoparticles of ~120 nm diameter has been realized via Stöber process and further functionalized using fluoroalkylsilane (FAS-17) molecules to incorporate the fluorinated groups with the silica nanoparticles in an ethanolic solution. The synthesized fluorinated silica nanoparticles have been spin coated on flat aluminum alloy, silicon and glass substrates. Functionalization of silica nanoparticles with fluorinated groups has been confirmed by Fourier Transform Infrared spectroscopy (FTIR) by showing the presence of C-F and Si-O-Si bonds. The water contact angles and surface roughness increase with the number of spin-coated thin films layers. The critical size of ~119 nm renders aluminum surface superhydrophobic with three layers of coating using as-prepared nanoparticle suspended solution. On the other hand, seven layers are required for a 50 vol.% diluted solution to achieve superhydrophobicity. In both the cases, water contact angles were more than 150°, contact angle hysteresis was less than 2° having a critical roughness value of ~0.700 µm. The fluorinated silica nanoparticle coated surfaces are also transparent and can be used as paint additives to obtain transparent coatings.

Surface Modification and Functionalization of Oxide Nanoparticles for Superhydrophobic Applications

Oxide nanoparticles have tremendous technological applications in the present days in diverse fields. In this study, the surface modification and functionalization of hydrophilic silica (SiO2) and zinc oxide (ZnO) nanoparticles were performed to obtain superhydrophobicity. Monodispersive nanoparticles of SiO2were prepared by Stöber process using tetraethoxysilane (Si (OC2H5)4) as a precursor and ammonium hydroxide as a catalyst in a ethanolic solution. The surface modification of the silica nanoparticles were performed using fluoroalkylsilane (FAS-17: C16H19F17O3Si) molecules to obtain fluorinated silica nanoparticles of diameter varying from 50nm to 300nm. On the other hand, surface modification of zinc oxide (ZnO) nanoparticles was performed using stearic acid (C18H36O2) molecules to obtain methylated ZnO nanoparticles. These functionalized nanoparticles were characterized both in the form of powder as well as thin films. The bonding characteristics of FAS-17 molecules with SiO2and stearic acid molecules with ZnO were investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Nanostructured thin films of these functionalized oxide nanoparticles exhibit superhydrophobicity with contact angles over 150° with water roll-off properties. Such functionalized oxides nanoparticles, therefore, can be easily incorporated in coatings and paints for various applications in emerging technologies like biomedical applications, anti-corrosion, anti-icing, drag reduction and energy consumption reduction.

Synthesis of Monodisperse Fluorinated Silica Nanoparticles and Their Superhydrophobic Thin Films

Monodispersive silica nanoparticles have been synthesized via the Stöber process and further functionalized by adding fluorinated groups using fluoroalkylsilane in an ethanolic solution. In this process, six different sizes of fluorinated silica nanoparticles of varying diameter from 40 to 300 nm are prepared and used to deposit thin films on aluminum alloy surfaces using spin coating processes. The functionalization of silica nanoparticles by fluorinated group has been confirmed by the presence C-F bonds along with Si-O-Si bonds in the thin films as analyzed by Fourier transform infrared spectroscopy (FTIR). The surface roughnesses as well as the water contact angles of the fluorinated silica nanoparticle containing thin films are found to be increased with the increase of the diameter of the synthesized fluorinated silica nanoparticles. The thin films prepared using the fluorinated silica nanoparticles having a critical size of 119 ± 12 nm provide a surface roughness of ∼0.697 μm rendering the surfaces superhydrophobic with a water contact angle of 151 ± 4°. The roughness as well as the water contact angle increases on the superhydrophobic thin films with further increase in the size of the fluorinated silica nanoparticles in the films.

New approach to fabricate an extremely super‐amphiphobic surface based on fluorinated silica nanoparticles

AbstractSuperoleophobic surfaces possessing static contact angles greater than 140° with organic liquids are extremely rare. A simple approach has been developed to fabricate an extremely superamphiphobic coating material based on fluorinated silica nanoparticles resulting contact angles of water and diiodomethane at 167.5° and 158.6°, respectively. The contact angle of diiodomethane at 158.6° is substantially higher than the highest literature reported value we know of at 110°. In addition, this developed film also possesses extremely high contact angles with other organic liquids such as soybean oil (146.6°), decahysronaphthalene (142.5°), diesel fuel (140.4°), and xylene (140.5°). This developed superamphiphobic organic–inorganic hybrid film possesses unique liquid repellency for both water and organic liquids that can be used as functional coatings on numerous substrates by a simple coating process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1984–1990, 2008

Use of surface plasmon-coupled emission for enhancing light transmission through Top-Emitting Organic Light Emitting Diodes

In this paper, we perform surface plasmon-coupled emission studies on Rhodamine 6G molecules embedded in a corrugated structure of a thin film composed of fluorinated silica particles, and a binding medium. Our results show enhancements of photoluminescence due to surface corrugation. By varying the size of the fluorinated silica nanoparticles we were able to control the surface correlation length scale of the corrugated surface structure. It was found that the coupling efficiency of the directional light emission is strongly correlated to the surface morphology, particularly the surface correlation length, of the corrugated dielectric structure. This substantial enhancement of signal could potentially be utilized in Organic Light Emitting Diode devices to enhance the light emission and transmission through a thin silver layer which can also serve as the cathode in Top-Emitting Organic Light Emitting Diodes.